Punctuated plastome reduction and host–parasite horizontal gene transfer in the holoparasitic plant genus
            Aphyllon

Foundational studies of chloroplast genome (plastome) evolution in parasitic plants have focused on broad trends across large clades, particularly among the Orobanchaceae, a species-rich and ecologically diverse family of root parasites. However, the extent to which such patterns and processes of plastome evolution, such as stepwise gene loss following the complete loss of photosynthesis (shift to holoparasitism), are detectable at shallow evolutionary time scale is largely unknown. We used genome skimming to assemble eight chloroplast genomes representing complete taxonomic sampling of Aphyllon sect. Aphyllon, a small clade within the Orobanchaceae that evolved approximately 6 Ma, long after the origin of holoparasitism. We show substantial plastome reduction occurred in the stem lineage, but subsequent change in plastome size, gene content, and structure has been relatively minimal, albeit detectable. This lends additional fine-grained support to existing models of stepwise plastome reduction in holoparasitic plants. Additionally, we report phylogenetic evidence based on an rbcL gene tree and assembled 60+ kb fragments of the Aphyllon epigalium mitochondrial genome indicating host-to-parasite horizontal gene transfers (hpHGT) of several genes originating from the plastome of an ancient Galium host into the mitochondrial genome of a recent common ancestor of A. epigalium . Ecologically, this evidence of hpHGT suggests that the host–parasite associations between Galium and A. epigalium have been stable at least since its subspecies diverged hundreds of thousands of years ago.

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The chloroplast genome evolution of Venus slipper (Paphiopedilum): IR expansion, SSC contraction, and highly rearranged SSC regions

BMC Plant Biology ◽

10.1186/s12870-021-03053-y ◽

2021 ◽

Vol 21 (1) ◽

Author(s):

Yan-Yan Guo ◽

Jia-Xing Yang ◽

Ming-Zhu Bai ◽

Guo-Qiang Zhang ◽

Zhong-Jian Liu

Keyword(s):

Gene Order ◽

Inverted Repeat ◽

Single Copy ◽

Gene Content ◽

Comparative Genomic ◽

Substitution Rates ◽

Plastome Evolution ◽

Chloroplast Genomes ◽

Ideal System ◽

Small Single Copy

Abstract Background Paphiopedilum is the largest genus of slipper orchids. Previous studies showed that the phylogenetic relationships of this genus are not well resolved, and sparse taxon sampling documented inverted repeat (IR) expansion and small single copy (SSC) contraction of the chloroplast genomes of Paphiopedilum. Results Here, we sequenced, assembled, and annotated 77 plastomes of Paphiopedilum species (size range of 152,130 – 164,092 bp). The phylogeny based on the plastome resolved the relationships of the genus except for the phylogenetic position of two unstable species. We used phylogenetic and comparative genomic approaches to elucidate the plastome evolution of Paphiopedilum. The plastomes of Paphiopedilum have a conserved genome structure and gene content except in the SSC region. The large single copy/inverted repeat (LSC/IR) boundaries are relatively stable, while the boundaries of the inverted repeat and small single copy region (IR/SSC) varied among species. Corresponding to the IR/SSC boundary shifts, the chloroplast genomes of the genus experienced IR expansion and SSC contraction. The IR region incorporated one to six genes of the SSC region. Unexpectedly, great variation in the size, gene order, and gene content of the SSC regions was found, especially in the subg. Parvisepalum. Furthermore, Paphiopedilum provides evidence for the ongoing degradation of the ndh genes in the photoautotrophic plants. The estimated substitution rates of the protein coding genes show accelerated rates of evolution in clpP, psbH, and psbZ. Genes transferred to the IR region due to the boundary shift also have higher substitution rates. Conclusions We found IR expansion and SSC contraction in the chloroplast genomes of Paphiopedilum with dense sampling, and the genus shows variation in the size, gene order, and gene content of the SSC region. This genus provides an ideal system to investigate the dynamics of plastome evolution.

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Endoparasitism in colonial hosts: patterns and processes

Parasitology ◽

10.1017/s0031182007002259 ◽

2007 ◽

Vol 134 (6) ◽

pp. 841-852 ◽

Cited By ~ 26

Author(s):

S. L. L. HILL ◽

B. OKAMURA

Keyword(s):

Vertical Transmission ◽

Environmental Conditions ◽

Negative Effects ◽

Temporal Sampling ◽

Colony Fission ◽

High Prevalence ◽

Novel Host ◽

Patterns And Processes ◽

Host Parasite ◽

Lack Of Knowledge

SUMMARYThis study begins to redress our lack of knowledge of the interactions between colonial hosts and their parasites by focusing on a novel host-parasite system. Investigations of freshwater bryozoan populations revealed that infection by myxozoan parasites is widespread. Covert infections were detected in all 5 populations studied and were often at high prevalence while overt infections were observed in only 1. Infections were persistent in populations subject to temporal sampling. Negative effects of infection were identified but virulence was low. Infection did not induce mortality in the environmental conditions studied. However, the production of statoblasts (dormant propagules) was greatly reduced in bryozoans with overt infections in comparison to uninfected bryozoans. Overtly-infected bryozoans also grew more slowly and had low fission rates relative to colonies lacking overt infection. Bryozoans with covert infections were smaller than uninfected bryozoans. High levels of vertical transmission were achieved through colony fission and the infection of statoblasts. Increased fission rates may be a strategy for hosts to escape from parasites but the parasite can also exploit the fragmentation of colonial hosts to gain vertical transmission and dispersal. Our study provides evidence that opportunities and constraints for host-parasite co-evolution can be highly dependent on organismal body plans and that low virulence may be associated with exploitation of colonial hosts by endoparasites.

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Hepatica transsilvanica Fuss (Ranunculaceae) is an Allotetraploid Relict of the Tertiary Flora in Europe – Molecular Phylogenetic Evidence

Acta Societatis Botanicorum Poloniae ◽

10.5586/asbp.8934 ◽

2020 ◽

Vol 89 (3) ◽

Cited By ~ 1

Author(s):

Levente Laczkó ◽

Gábor Sramkó

Keyword(s):

Parental Species ◽

Gene Tree ◽

Diploid Species ◽

Nuclear Gene ◽

Hybrid Origin ◽

Distribution Area ◽

Recent Common Ancestor ◽

Term Survival ◽

Quaternary Glaciation ◽

Eastern Carpathians

The Hepatica section Angulosa consists of mainly tetraploid (2n = 28) species that are distributed disjunctly throughout Eurasia. Karyological evidence proves the hybrid origin of the polyploid species of this section. Hepatica transsilvanica is a member of this species group with a conspicuous distribution restricted to the Eastern Carpathians. Based on genome size and cytotypes, the paternal parent of H. transsilvanica is described to be the only diploid species in section Angulosa, H. falconeri. The maternal species is hypothesized to be H. nobilis, a European species with entirely lobed leaves and a wider distribution area. Although the hybrid origin of H. transsilvanica is well documented by karyological evidence, the time of hybridization has never been studied. By using sequences of both the nuclear and plastid genome, we reconstructed the phylogenetic relationships and divergence times of H. transsilvanica and its parental species. The identity of the parental species is corroborated by discordant gene tree topologies of the nrITS and plastid sequences. Moreover, both gene copies of the parental species could be identified with the low-copy nuclear gene, MLH1. Divergence dating analysis using Bayesian phylogenetic methods strongly supported the long-term survival of H. transsilvanica in the Southeastern Carpathians, as the most recent common ancestor of the hybrid and parent species existed not later than the beginning of the Pleistocene, ca. 3 million years ago. These results not only highlight the biogeographic importance of the Southeastern Carpathians in the Quaternary glaciation periods, but also emphasize that Tertiary lineages could have survived in a Central European cryptic refugium.

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Phylogenetic and Comparative Analyses of Complete Chloroplast Genomes of Chinese Viburnum and Sambucus (Adoxaceae)

Plants ◽

10.3390/plants9091143 ◽

2020 ◽

Vol 9 (9) ◽

pp. 1143 ◽

Cited By ~ 1

Author(s):

Hang Ran ◽

Yanyan Liu ◽

Cui Wu ◽

Yanan Cao

Keyword(s):

Genomic Structure ◽

Phylogenetic Analyses ◽

Sister Relationship ◽

Plastome Evolution ◽

Chloroplast Genomes ◽

Flora Of China ◽

Phylogenetic Resolution ◽

Sister Relationships ◽

Phylogenomic Analyses ◽

Cp Genome

Phylogenetic analyses of complete chloroplast genome sequences have yielded significant improvements in our understanding of relationships in the woody flowering genus Viburnum (Adoxaceae, Dipsacales); however, these relationships were evaluated focusing only on Viburnum species within Central and South America and Southeast Asia. By contrast, despite being a hotspot of Viburnum diversity, phylogenetic relationships of Viburnum species in China are less well known. Here, we characterized the complete chloroplast (cp) genomes of 21 Viburnum species endemic to China, as well as three Sambucus species. These 24 plastomes were highly conserved in genomic structure, gene order and content, also when compared with other Adoxaceae. The identified repeat sequences, simple sequence repeats (SSRs) and highly variable plastid regions will provide potentially valuable genetic resources for further population genetics and phylogeographic studies on Viburnum and Sambucus. Consistent with previous combined phylogenetic analyses of 113 Viburnum species, our phylogenomic analyses based on the complete cp genome sequence dataset confirmed the sister relationship between Viburnum and the Sambucus-Adoxa-Tetradoxa-Sinadoxa group, the monophyly of four recognized sections in Flora of China (i.e., Viburnum sect. Tinus, Viburnum sect. Solenotinus, Viburnum sect. Viburnum and Viburnum sect. Pseudotinus) and the nonmonophyly of Viburnum sect. Odontotinus and Viburnum sect. Megalotinus. Additionally, our study confirmed the sister relationships between the clade Valvatotinus and Viburnum sect. Pseudotinus, as well as between Viburnum sect. Opulus and the Odontotinus-Megalotinus group. Overall, our results clearly document the power of the complete cp genomes in improving phylogenetic resolution, and will contribute to a better understanding of plastome evolution in Chinese Adoxaceae.

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Phylogenetic Analysis and Substitution Rate Estimation of Colonial Volvocine Algae Based on Mitochondrial Genomes

Genes ◽

10.3390/genes11010115 ◽

2020 ◽

Vol 11 (1) ◽

pp. 115

Author(s):

Yuxin Hu ◽

Weiyue Xing ◽

Zhengyu Hu ◽

Guoxiang Liu

Keyword(s):

Phylogenetic Analysis ◽

Mitochondrial Genome ◽

Phylogenetic Relationship ◽

Phylogenetic Analyses ◽

Mitochondrial Protein ◽

Substitution Rates ◽

Protein Coding ◽

Protein Coding Genes ◽

Chloroplast Genomes ◽

Volvocine Algae

We sequenced the mitochondrial genome of six colonial volvocine algae, namely: Pandorina morum, Pandorina colemaniae, Volvulina compacta, Colemanosphaera angeleri, Colemanosphaera charkowiensi, and Yamagishiella unicocca. Previous studies have typically reconstructed the phylogenetic relationship between colonial volvocine algae based on chloroplast or nuclear genes. Here, we explore the validity of phylogenetic analysis based on mitochondrial protein-coding genes. We found phylogenetic incongruence of the genera Yamagishiella and Colemanosphaera. In Yamagishiella, the stochastic error and linkage group formed by the mitochondrial protein-coding genes prevent phylogenetic analyses from reflecting the true relationship. In Colemanosphaera, a different reconstruction approach revealed a different phylogenetic relationship. This incongruence may be because of the influence of biological factors, such as incomplete lineage sorting or horizontal gene transfer. We also analyzed the substitution rates in the mitochondrial and chloroplast genomes between colonial volvocine algae. Our results showed that all volvocine species showed significantly higher substitution rates for the mitochondrial genome compared with the chloroplast genome. The nonsynonymous substitution (dN)/synonymous substitution (dS) ratio is similar in the genomes of both organelles in most volvocine species, suggesting that the two counterparts are under a similar selection pressure. We also identified a few chloroplast protein-coding genes that showed high dN/dS ratios in some species, resulting in a significant dN/dS ratio difference between the mitochondrial and chloroplast genomes.

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Effect of prolonged vegetative reproduction of olive tree cultivars (Olea europaea L.) in mitochondrial homoplasmy and heteroplasmy

Genome ◽

10.1139/g03-017 ◽

2003 ◽

Vol 46 (3) ◽

pp. 377-381 ◽

Cited By ~ 15

Author(s):

Angel García-Díaz ◽

Ricardo Oya ◽

Antonio Sánchez ◽

Francisco Luque

Keyword(s):

Mitochondrial Genome ◽

Sexual Reproduction ◽

Olea Europaea ◽

Vegetative Reproduction ◽

Intergenic Spacer Region ◽

Olea Europaea L ◽

Chloroplast Genomes ◽

Mitochondrial Region ◽

Olive Trees ◽

Olea Europaéa

The inheritance of mitochondrial and chloroplast genomes does not follow Mendelian laws, but proceeds by vegetative segregation. Most organisms show organelle homoplasmy, which is probably produced and maintained during sexual reproduction. We have tested the effect of prolonged vegetative multiplication in the maintenance of mitochondrial homoplasmy and the generation of heteroplasmy in cultivated olive trees, Olea europaea L. Seven trees, each representing a different variety of olive, were analysed by the study of an intergenic spacer region of the mitochondrial genome. A very high level of heteroplasmy was detected in all cases. We found multiple genome variants of the sequence analysed. The frequency of genomes with no changes in the spacer region was 11.5%. This means that 88.5% of genomes contain at least one change. The same spacer mitochondrial region was sequenced in several clones from four olive trees of a second generation of sexually reproduced trees. In these trees, many clones were identical and had no changes, which represents a clear reduction of the heteroplasmy (p < 0.001). Therefore, this work supports the relevance of the role of sexual reproduction in the maintenance of mitochondrial homoplasmy and also shows that mutations accumulate in a non-coding sequence of the mitochondrial genome when vegetative propagation is maintained for a long period of time.Key words: mitochondrial genome, homoplasmy, heteroplasmy, olive trees, vegetative reproduction, sexual reproduction.

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Ascaridoid nematodes of amphibians and reptiles: Angusticaecum and Krefftascaris n.g.

Journal of Helminthology ◽

10.1017/s0022149x00006350 ◽

1980 ◽

Vol 54 (1) ◽

pp. 55-73 ◽

Cited By ~ 12

Author(s):

J. F. A. Sprent

Keyword(s):

New Species ◽

North Africa ◽

New Genus ◽

Natural State ◽

Freshwater Turtles ◽

Evolutionary Time ◽

Eastern Australia ◽

Host Parasite ◽

A New Species

ABSTRACTAscaridoid nematodes reported from terrestrial and freshwater chelonians are described under two monotypic genera, Angusticaecum and a new genus Krefftascaris respectively. The former genus contain A. holopterum (Rodolphi, 1819) Baylis, 1920 [synonym A. brevispiculum Chapin, 1924], reported in the natural state from testudinid and emydid tortoises in Europe, U.S.S.R., Iran, Brazil and North Africa. Teh latter genus contains a new species, K. parmenteri, reported from chelid freshwater turtles in Eastern Australia. It is concluded that the former is most closely related to species in other genera in terrestrial reptiles, whereas the latter is closest to Gedoelstascaris spp. in crocodilians. Host-parasite relationships over evolutionary time between ascaridoids and chelonians are discussed.

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Complete Mitochondrial Genomes of Three Mangifera Species, Their Genomic Structure And Gene Transfer From Chloroplast Genomes

10.21203/rs.3.rs-1059761/v1 ◽

2021 ◽

Author(s):

Yingfeng Niu ◽

Chengwen Gao ◽

Jin Liu

Keyword(s):

Mitochondrial Genome ◽

Genomic Structure ◽

Mangifera Indica ◽

Gene Content ◽

Rrna Genes ◽

Mitochondrial Genomes ◽

Trna Genes ◽

Protein Coding ◽

Protein Coding Genes ◽

Chloroplast Genomes

Abstract BackgroundAmong the Mangifera species, mango (Mangifera indica) is an important commercial fruit crop. However, very few studies have been conducted on the Mangifera mitochondrial genome. This study reports and compares the newly sequenced mitochondrial genomes of three Mangifera species. Results Mangifera mitochondrial genomes showed partial similarities in the overall size, genomic structure, and gene content. Specifically, the genomes are circular and contain about 63-69 predicted functional genes, including five ribosomal RNA (rRNA) genes and 24-27 transfer RNA (tRNA) genes. The GC contents of the Mangifera mitochondrial genomes are similar, ranging from 44.42–44.66%. Leucine (Leu) and serine (Ser) are the most frequently used, while tryptophan (Trp) and cysteine (Cys) are the least used amino acids among the protein-coding genes in Mangifera mitochondrial genomes. We also identified 7-10 large chloroplast genomic fragments in the mitochondrial genome, ranging from 1407-6142 bp. Additionally, four intact mitochondrial tRNAs genes (tRNA-Cys, tRNA-Trp, tRNA-Pro, and tRNA-Met) and intergenic spacer regions were identified. Phylogenetic analysis based on the common protein-coding genes of most branches provided a high support value. ConclusionsWe sequenced and compared the mitochondrial genomes of three Mangifera species. The results showed that the gene content of Mangifera mitochondrial genomes is similar across various species. Gene transferred from the chloroplast genome to the mitochondrial genome were identified. This study provides valuable information for evolutionary and molecular studies of Mangifera and a basis for further studies on genomic breeding of mango.

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Unraveling heteroplasmy patterns with NOVOPlasty

NAR Genomics and Bioinformatics ◽

10.1093/nargab/lqz011 ◽

2019 ◽

Vol 2 (1) ◽

Cited By ~ 4

Author(s):

Nicolas Dierckxsens ◽

Patrick Mardulyn ◽

Guillaume Smits

Keyword(s):

Mitochondrial Genome ◽

Open Source Software ◽

High Frequency ◽

Mitochondrial Haplotype ◽

Benchmark Study ◽

Haplotype Allele ◽

Mitochondrial Haplotypes ◽

Chloroplast Genomes ◽

Technological Advances ◽

Scientific Fields

Abstract Heteroplasmy, the existence of multiple mitochondrial haplotypes within an individual, has been studied across different scientific fields. Mitochondrial genome polymorphisms have been linked to multiple severe disorders and are of interest to evolutionary studies and forensic science. Before the development of massive parallel sequencing (MPS), most studies of mitochondrial genome variation were limited to short fragments and to heteroplasmic variants associated with a relatively high frequency (>10%). By utilizing ultra-deep sequencing, it has now become possible to uncover previously undiscovered patterns of intra-individual polymorphisms. Despite these technological advances, it is still challenging to determine the origin of the observed intra-individual polymorphisms. We therefore developed a new method that not only detects intra-individual polymorphisms within mitochondrial and chloroplast genomes more accurately, but also looks for linkage among polymorphic sites by assembling the sequence around each detected polymorphic site. Our benchmark study shows that this method is capable of detecting heteroplasmy more accurately than any method previously available and is the first tool that is able to completely or partially reconstruct the sequence for each mitochondrial haplotype (allele). The method is implemented in our open source software NOVOPlasty that can be downloaded at https://github.com/ndierckx/NOVOPlasty.

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Comparison and Phylogenetic Analyses of Nine Complete Chloroplast Genomes of Zingibereae

Forests ◽

10.3390/f12060710 ◽

2021 ◽

Vol 12 (6) ◽

pp. 710

Author(s):

Heng Liang ◽

Juan Chen

Keyword(s):

Ribosomal Rna ◽

Phylogenetic Analyses ◽

Plastome Evolution ◽

Chloroplast Genomes ◽

The Family ◽

Phylogenomic Analyses ◽

Close Relatives ◽

Rna Genes ◽

Insight Into ◽

Simple Sequence

Zingibereae is a large tribe in the family Zingiberaceae, which contains plants with important medicinal, edible, and ornamental values. Although tribes of Zingiberaceae are well circumscribed, the circumscription of many genera within Zingibereae and the relationships among them remain elusive, especially for the genera of Boesenbergia, Curcuma, Kaempferia and Pyrgophyllum. In this study, we investigated the plastome variation in nine species representing five genera of Zingibereae. All plastomes showed a typical quadripartite structure with lengths ranging from 162,042 bp to 163,539 bp and contained 132–134 genes, consisting of 86–88 coding genes, 38 transfer RNA genes and eight ribosomal RNA genes. Moreover, the characteristics of the long repeats sequences and simple sequence repeats (SSRs) were detected. In addition, we conducted phylogenomic analyses of the Zingibereae and related taxa with plastomes data from additional 32 species from Genbank. Our results confirmed that Stahlianthus is closely related to Curcuma, supporting the idea of merging it into Curcuma. Kaempferia, Boesenbergia and Zingiber were confirmed as close relatives and grouped together as the Kaempferia group. Pyrgophyllum is not allied with the Curcuma clade but instead is embedded within the Hedychium clade. Our results demonstrate the power of plastid phylogenomics in improving the phylogenetic relationships within Zingibereae and provide a new insight into plastome evolution in Zingibereceae.

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